Medicinal plants and medical plant materials that contain tannic substances

Tannins are astringent, bitter plant polyphenols that either bind and precipitate or shrink proteins.  The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine.   Tannins are polyphenolic secondary metabolites of higher plants, and are either galloyl esters and their derivatives, in which galloyl moieties or their derivatives are attached to a variety of polyol-, catechin and triterpenoid cores (gallotannins, ellagotannins and complex tannins), or they are oligomeric and polymeric proantocyanidins that can possess different interflavanyl coupling and substitution patterns (condensed tannins).

Gallic acid The word tannin is very old and reflects a traditional technology. "Tanning" (waterproofing and preserving) was the word used to describe the process of transforming animal hides into leather by using plant extracts from different plant parts of different plant species.

HHDP – hexahydroxy diphenic acid

Classification of tannins I. Procter’s classification (1894): Tannins decompose at degree (without air) and yield pyrogallol, pyrocatechin. PyrogallolPyrocatechin

Two main groups of tannins are usually recognized; these are the hydrolysable tannins and the condensed tannins (proanthocyanidins).

Hydrolysable tannins

They may be hydrolysed by acids or enzymes such as tannase. They are formed from several molecules of phenolic acids such as gallic and hexahydroxydiphenic acids which are united by ester linkages to a central glucose molecule. Gallic acid

Three principal types of hydrolysable tannins are:  - gallitannins (ethers of gallic acid and sugars);  - ellagitannins (ethers of hexahydroxydiphenic (ellagic) acid and sugars);  - non-sugar ethers of phenolcarbolic acids(quinic acid).

Condensed tannins (proanthocyanidins)

Unlike hydrolysable tannins, these are not readily hydrolysed to simpler molecules and they do not contain a sugar moiety. They are related to the flavonoid pigments and have polymeric flavan-3-ol structures. Flavone

They are divided into 3 groups as well:  - derivatives of flavanols-3;  - derivatives of flavandiols-3,4;  - derivatives of oxystilbens (diphenilethylene).

Occurrence of tannins Tannins are of wide occurrence in plants and are usually found in greatest quantity in dead or dying cells. They exert an inhibitory effect on many enzymes due to protein precipitation and, hence, they may contribute a protective function in barks and heartwoods. Tannins are of wide occurrence in plants and are usually found in greatest quantity in dead or dying cells. They exert an inhibitory effect on many enzymes due to protein precipitation and, hence, they may contribute a protective function in barks and heartwoods.

Properties and tests  Tannins are soluble in water, dilute alkalis, glycerol and acetone, but generally only sparingly soluble in other organic solvents. Solutions precipitate heavy metals, alkaloids, glycosides and gelatin.  Tannins can be extracted with hot water, and after that extract should be purified by chlorophorm, diethyl ether and ethyl acetate respectively.

Identification  Gelatin test. Solutions of tannins precipitate a solution of gelatin.  Tannins also precipitate alkaloids.  With iron-ammonium alum, hydrolysable T. give blue-black colour and condensed T. brownish-green colour.  Condensed T. with vanillin and concentrated hydrochloric acid or 70% sulfuric acid give red colour.

 With lead acetate in acetic acid hydrolysable tannins precipitate, and condensed stay in solution.  Free ellagic acid can be identified by adding several chrystals of sodium nitrate and 3-4 drops of acetic acid, a red-violet colour develops.  Bound ellagic acid (HHDP) can be determined with sodium nitrate and 0,1hydrochloric or 0,1 sulfuric acid. Develops red colour which becomes blue.  Chromatography is used to identify low- molecular tannins.

Biological action and uses of tannins  Tannins may be employed medicinally in antidiarrheal, haemostatic, and antihaemorrhoidal compounds.  The anti-inflammatory effect of tannins helps control all indications of gastritis, esophagitis, enteritis, and irritating bowel disorders. Diarrhea is also treated with an effective astringent medicine that does not stop the flow of the disturbing substance in the stomach; rather, it controls the irritation in the small intestine.  Tannins not only heal burns and stop bleeding, but they also stop infection while they continue to heal the wound internally. The ability of tannins to form a protective layer over the exposed tissue keeps the wound from being infected even more. Tannins are also beneficial when applied to the mucosal lining of the mouth.

 They have also been reported to have anti-viral effects. When incubated with red grape juice and red wines with a high content of condensed tannins, the poliovirus, herpes simplex virus, and various enteric viruses are inactivated.  Tannins can also be used to pull out poisons from poison oak or from bee stings, causing instant relief. The tannins help draw out all irritants from the skin because tannin is an astringent that tightens pores and pulls out liquids.

MP and MPM containing tannins

Sumach leaf – Rhois coriariae folia Rhus coriaria- Sumach, Sicilian sumac Anacardiaceae (cashew or sumac family) Constituents. Sumac leaves contain 13-25% of tannins, flavonoids, ether oil, ascorbic acid. Uses. Sumac leaves are used to get tannin, which is part of “Galascorbin” and Novikov’s liquid.

Smoke tree leaf – Cotini coggygriae Folia Cotinus coggygria- Common Smoketree, Smokebush Anacardiaceae  Constituents. Gallotannin, flavonoids, volatile oils  Uses. Medicines- Galascorbin has astringent and P-vitaminic action, Flacumin, which contains up to 75% of flavonoids and has cholagogue action.

Bergenia rhizome – Bergeniae Rhizomata Bergenia crassifolia – Badan, Elephant’s ears, Siberian tea Saxifragaceae  Constituents. MPM contains blend of gallotannins and condensed tannins (21-25%), arbutin (up to 5%), katekhin, gallic acid, traces of rutin and quercetin  Uses. Decoction is used to treat infectious colitis and enterocolitis, externally- to treat mouth ulcers. In gynaecology- to treat cervical erosion

Alder fruit – Alni Fructus Alnus incana, alnus glutinosa – Grey or Speckled Alder Alnus glutinosa- Black Alder, European Alder or Common Alder Betulaceae  Constituents. MPM contains ellagotannins, gallotannins, free gallic and ellagic acids up to 15%.  Uses. Fruits are used as astringent, anti-inflammatory and haemostatic agent; they are part of stomach mixes, “Kamilal” (suppositories). “Altan” is used as anti-inflammation and pain- killing drug to treat indigestion

Oak bark – QuercusCortex Quercus robur- Pedunculate Oak or English oak Fagaceae  Constituents. Bark contains tannins, mainly of condensed type (12%), free gallic and ellagic acids, flavonoids, saponins, carbohydrates.  Uses. Oak bark is used medicinally for its astringent and anti-inflammation properties to treat gingivitis and stomatitis, burns and frostbite. Oak bark is included to anti- haemorrhoidal mixes and complex medicines.

Bilberry leaf, fruit – Myrtilli Fructus Myrtilli Folia Vaccinium myrtillus- Bilberry Ericaceae (Heather family)  Constituents. Fruits contain condensed tannins (12%); anthocyanidins, organic acids, carotene, pectin. Leaves contain condensed tannins (7-20%), phenols- neomyrtillin, myrtillin (2%), arbutin (1%), flavonoids. Leaves contain condensed tannins (7-20%), phenols- neomyrtillin, myrtillin (2%), arbutin (1%), flavonoids.  Uses. Fruits are used as mild astringent agent to treat diarrhea in children and acute enterocolitis in adults. Myrtillin reduces sugar level in blood and thus is part of antidiabetics collection “Arphazetin”.